On Thu, 10 May 2018 14:28:37 -0700 Jane Wan <jane....@nokia.com> wrote:
> Per ONFI specification (Rev. 4.0), if all parameter pages have invalid > CRC values, the bit-wise majority may be used to recover the contents of > the parameter pages from the parameter page copies present. > > Signed-off-by: Jane Wan <jane....@nokia.com> > --- > v6: support the cases that srcbufs are not contiguous > v5: make the bit-wise majority functon generic > v4: move the bit-wise majority code in a separate function > v3: fix warning message detected by kbuild test robot > v2: rebase the changes on top of v4.17-rc1 > > drivers/mtd/nand/raw/nand_base.c | 52 > ++++++++++++++++++++++++++++++++++---- > 1 file changed, 47 insertions(+), 5 deletions(-) > > diff --git a/drivers/mtd/nand/raw/nand_base.c > b/drivers/mtd/nand/raw/nand_base.c > index 72f3a89..acf905c 100644 > --- a/drivers/mtd/nand/raw/nand_base.c > +++ b/drivers/mtd/nand/raw/nand_base.c > @@ -5087,6 +5087,35 @@ static int nand_flash_detect_ext_param_page(struct > nand_chip *chip, > } > > /* > + * Recover data with bit-wise majority > + */ > +static void nand_bit_wise_majority(const void **srcbufs, > + unsigned int nsrcbufs, > + void *dstbuf, > + unsigned int bufsize) > +{ > + int i, j, k; > + > + for (i = 0; i < bufsize; i++) { > + u8 cnt, val; > + > + val = 0; > + for (j = 0; j < 8; j++) { > + cnt = 0; > + for (k = 0; k < nsrcbufs; k++) { > + const u8 *srcbuf = srcbufs[k]; > + > + if (srcbuf[i] & BIT(j)) > + cnt++; > + } > + if (cnt > nsrcbufs / 2) > + val |= BIT(j); > + } > + ((u8 *)dstbuf)[i] = val; > + } > +} > + > +/* > * Check if the NAND chip is ONFI compliant, returns 1 if it is, 0 otherwise. > */ > static int nand_flash_detect_onfi(struct nand_chip *chip) > @@ -5102,7 +5131,7 @@ static int nand_flash_detect_onfi(struct nand_chip > *chip) > return 0; > > /* ONFI chip: allocate a buffer to hold its parameter page */ > - p = kzalloc(sizeof(*p), GFP_KERNEL); > + p = kzalloc((sizeof(*p) * 3), GFP_KERNEL); > if (!p) > return -ENOMEM; > > @@ -5113,21 +5142,34 @@ static int nand_flash_detect_onfi(struct nand_chip > *chip) > } > > for (i = 0; i < 3; i++) { > - ret = nand_read_data_op(chip, p, sizeof(*p), true); > + ret = nand_read_data_op(chip, &p[i], sizeof(*p), true); > if (ret) { > ret = 0; > goto free_onfi_param_page; > } > > - if (onfi_crc16(ONFI_CRC_BASE, (uint8_t *)p, 254) == > + if (onfi_crc16(ONFI_CRC_BASE, (u8 *)&p[i], 254) == > le16_to_cpu(p->crc)) { > + if (i) > + memcpy(p, &p[i], sizeof(*p)); > break; > } > } > > if (i == 3) { > - pr_err("Could not find valid ONFI parameter page; aborting\n"); > - goto free_onfi_param_page; > + const void *srcbufs[3] = {p, p + 1, p + 2}; > + > + pr_err("Could not find valid ONFI parameter page\n"); Maybe pr_warn() here > + pr_info("Recover ONFI params with bit-wise majority\n"); and maybe you can pack the 2 messages: pr_warn("Could not find a valid ONFI parameter page, trying bit-wise majority to recover it"); > + > + nand_bit_wise_majority(srcbufs, ARRAY_SIZE(srcbufs), p, > + sizeof(*p)); > + > + if (onfi_crc16(ONFI_CRC_BASE, (u8 *)p, 254) != > + le16_to_cpu(p->crc)) { > + pr_err("ONFI parameter recovery failed, aborting\n"); > + goto free_onfi_param_page; > + } > } > > /* Check version */